Manufacture of tile for acoustic and decorative effects



July 7, 1964 E. BERSET 3,140,331

MANUFACTURE OF TILE FOR ACOUSTIC AND DECORATIVE EFFECTS Filed April 1,1959 INVENTOR.

Edward Bersel M/ {J m W Jizorney holes of uniform size or differentsizes.

United States Patent UFACTURE OF TILE FOR ACOUSTIC AND DECORATIVEEFFECTS Edward Berset, Cloquet, Minn, assignor to Wo'od ConversionCompany, St. Paul, Minn, a corporation of Delaware Filed Apr. 1, 1959,Ser. No. 803,523 4 Claims. (Cl. 264-493) The present invention relatesto the production of tile from felted fiber panel, and in particular toprocesses for treating the tile face, either for acoustic purposes, orfor decorative effect, or both.

Such tile is commonly provided in squares, cut from larger panels whichare produced by felting an aqueous slurry of vegetable fibers, forexample, on a Fourdrinier machine. Wet felts are pressed and dried. Theprocessing produces various stresses in the dry panel. When the panel iscut into smaller squares some stresses are released. As a result, manytile squares have varying perceptible warp.

The final tile is coated usually by coating the panel before the tile iscut from it. The coat may be applied in whole or in part to the pressedwet felt before drying, or in whole or in part to the panel afterpressing the wet felt and drying. In some operations, a prime coat isapplied to the pressed wet felt, and after drying, a top coat isapplied. The coat and the coating process also introduce stressesleading to perceptible warp. Special treatments in processing the panelmay be practiced to insure a predetermined direction of warp such thatsubsequent processing of tile cut from the panel tend to correct thewarp.

Acoustic tile of numerous well-known brands having vegetable fiberbodies, is made by drilling or punching a multiplicity of holes into drycoated tile, in a regular pattern, or in a random pattern, and in eachcase with It has been observed that the drilling or punching process asheretofore practiced changed the stress patterns within the tile andthis also contributes to warp. When this processing leads to negativewarp, which is a dishing of the exposable face, the panel may beprocessed to introduce positive warp in the tile square cut from it, inorder to decrease or eliminate the positive warp by processing the tile.

Other forms of tile are produced for decorative purposes by impressingdesign patterns into a final coated tile or uncoated tile, orprime-coated tile. Coating material may be applied after the design isimpressed. Hot platens and steam or moisture are commonly used to softenthe board or coat, or both, thereby to facilitate the impressing actionas Well as to avoid breaking or cracking an applied coat at certaincritical boundaries of the design areas. These operations of impressing,and of coating after impressing also pertain to stresses leading towarp.

The processing of tile as above described constitutes substantiallyuniform loading of pressure on the exposable face. For acoustical tilethis is effected by the numerous drills or punches applied oversubstantially the entire face of the tile. In the case of tile withimpressed designs, it is the pressing platen which applies the load.

Whether the tiles to be processed are unwarped or warped, the processingdescribed tends to produce a negative warp, of which the direction ofwarp is such as to 3,140,331 Patented July 7, 1964 cup or dish theexposable processed face of the tile. Although the warp in a single tilemay be almost imperceptible, a ceiling assembly of tiles inevitablyevidences that warp when viewed at certain angles to receive reflectionsfrom one or more sources of light which are more or less pin-pointed.The more nearly planar all the tile are made, the better a ceilingassembly will be.

In studying the various decorative and acoustic tile above referred to,it was observed that the tile blanks to be processed are placed with theback side on a flat platen. In processing, the face is substantiallyuniformly loaded and compressed toward said platen. This results incompression of the tile between its faces. If the tile blank to beprocessed is already warped to a dished face, such compression merelyflattens it temporarily. But, during the compression other changes takeplace. The holes formed cut through material of the panel and any coatthereon and over the area of the hole release any stress of tension orcompression. Especially when the holes terminate within the panel, thechange in stress is more limited to the face than to the back of thetile. Thus, an originally warped or planar tile blank acquires atendenecy to warp negatively merely by forming holes therein foracoustic purposes.

In the case of impressing designs in the tile face, the back hasheretofore been placed on a flat platen, and a die-plate embossed with anegative of the pattern is pressed onto the tile to leave an impression.The operation is best performed with a heated plate, which is effectiveon heat-softenable coats. Moisture in the form of water or steam alsofacilitates the process. The moisture may soften both the coat and thefibers of the body with or without a surface coat. These factors ofmechanical pressure varying With the pattern, the moisture and the heat,change old stresses and introduce new stresses, leading to warping ofthe tile to a dished face.

. The present invention aims to introduce new and antiwarping stressesin a finshed tile by certain straining of the tile.

Accordingly, it is an object of the invention so to strain a tile thatthe warping tendencies of original stresses are modified or eliminatedand that new stresses are introduced tending to hold the finished tilein a generally fiat condition.

It is a particular object so to strain the tile during the processing ofthe face as above referred to.

Various other and ancillary objects and advantages of the invention willappear from the following description and expalantion given inconnection with the accompanying drawing, in which:

FIG. 1 illustrates partly in cross-section and in perspective, a tilepositioned for processing between a Support and a pressing member.

FIGS. 2 and 3 represent two pyramidal inserts for supporting the backsof tile processed at the face.

FIG. 4 is a stepped pyramid of concentric squares.

FIG. 5 is an enlarged fragmentary cross-section taken on line 55 of FIG.4.

In carrying out the invention the back of the tile is placed on asupporting platen which is slightly crowned centrally so as to be highin the center with its four edges similarly at a lower level or levels,thus to effect a dished contour on the back face of a tile whilecompressed onto the platen by any type of substantially uniform loadingof the face. The crowned platen is preferably symmetrical 3 with respectto two right-angular axes, as when it is spherically convex, pyramidalwith sides in number which is 4 or a multiple of 4, or a pile ofso-centered polygons of thin sheets reducing in size and having sides innumber which is 4 or a multiple thereof. Minor departures from suchregularity are permissible so long as a generally uniform crowningexists.

Without need to change the hole-forming operation or thedesign-impressing action, the tile is pressed onto the crowned platen bymeans at the face, which pressing may be a planar or embossed platen ora bank of drills or punches. As a result, the back of the tile duringsuch compression is dished to match the crowned platen, by thinning thetile at the center more than at its edges. The stresses thus introducedand retained on release of the tile from the operating compression,counter the tendencies to warp the face into slightly dished form.

The following exemplifies conditions heretofore encountered with acoated wood fiber tile 12-inches square, /2 inch thick, and with adensity of 17 lbs. per cu. ft. When drilling 319 holes into it usinghollow drills inch or Ai-inch in diameter, or the two sizes mixed, ithas been found that the entrance pressure and the drilling pressure perdrill are high, as shown in Table I.

With over 300 drills, the total pressure is very high but distributedand centered at many local areas. This operation carried out asdescribed on a planar supporting platen creates on release a dished warpin the face with the tile center inwardly from the boundary of its edgesby an amount varying in the range from .015 to .025 inch.

In the debossing operation above described, the results vary withnumerous factors, including the design and its local areas, the depth ofdesign components, the platen pressure and temperature, the coat if any,and the amount of moisture if any.

Because titles vary in the degree of warp from one to another even whenout from the same panel, coated or not, the invention contemplatesreducing the tendency of all the title by similarly processing them, itbeing understood that perfection to that end result can be effected insome cases. In consequence, the crowning of the supporting platen isfixed at that which produces satisfactory average results for each typeof panel material.

It has been found that with the wood fiber panel above described, agiven crowning of a supporting platen is satisfactory in both a drillingor punching operation of the kind described, and in a hot-debossingoperation as described.

To achieve the desired result, and to practice the invention, an insertwhich is flat on one face and crowned on the other is placed on the fiatsupporting platen heretofore used.

In the drawing, the numeral 10 represents a flat supporting platen, suchas used heretofore to receive the title, on which is placed aplano-convex insert 11. A guiding frame for locating the tile isillustrated by the cross-section of three of its members 12, 13 and 14.The tile 15 is shown in the frame. The dotted line block 16 above thetile represents the pressing element or operation being either a planarplaten, or a bank of drills or punches or a platen with an embossednegative of a design. Arrow 17 represents movement of plate 16.

With reference to a 12-inch square tile, as described, a satisfactoryinsert platen is one ljnimches square, with plane face 13, sphericallyconvex face 19, with edges 0.020-incl1 at maximum thickness, and center0.085-inch thick, resulting in a differential of 0.065-inch for theinsert, nearly all of which is applied to the tile in process.

FIG. 2 shows a pyramidal insert 21 of four similar sides 22. When thecenter crowning is the same as described for insert 11 it may besubstituted for insert 11.

FIGS. 3 and 4 show substitute inserts of the same degree of crowning.FIG. 3 shows a pyramid 24 of eight similar sides 25.

FIG. 4 shows an insert 26 of concentric squares of upwardly decreasingsize to effect the desired crowning. It has th thicker base 27, and onits four thin layers 28 to 31 of approximately .0l6-inch thickness. Thebase 27 may be wood, hardboard or metal. The layers 28 to 31 may bemetal or fiber sheets, the latter being preferred so that the indicatedexposed square edges 32 (FIG. 5) thereof may be rounded off as indicatedto avoid ridge marks in the back if desired.

In other words, by the present invention the tile is so stressed that inthe release of stresses, the movement may still be in the direction todish the face of the tile, but the movement is from a reverse of theundesired condition so as to stop in the vicinity of the desired planarform, rather than movement away from a planar form into undesired warp.

As examples of debossing designs in tile, see design patents Des.183,531, and Des. 183,697. The drilling and the debossing alter thestresses in the face. The debossing of designs moves portions of theface to inward locations such that on release of the compression inwardlocations remain.

I claim:

1. The method of treating a substantially square tile of porousfiberboard useful as ceiling tile, which comprises compressing the tileonto a centrally crowned supporting platen by applying a substantiallyplanar platen and thereby substantially uniformly loading the exposabletile face, whereby during compression to deform the tile to a dishedback surface corresponding generally to said crowned platen and therebyaltering the original stresses in the uncompressed tile and introducingnew stresses in the compressed tile, and releasing the tile from saidcompression.

2. The method of treating a substantially square tile of porousfiberboard useful as ceiling tile, which comprises compressing the tileonto a centrally crowned supporting platen by applying a heatedsubstantially planar platen embossed with a design and therebyhot-pressing portions of the surface to inward locations and therebysubstantially uniformly loading the exposable tile face, whereby duringcompression to deform the tile to a dished back surface correspondinggenerally to said crowned platen and thereby altering the originalstresses in the uncompressed tile and introducing new stresses in thecompressed tile, and releasing the tile from said compression, saidinward locations being such that on said release of compression inwardlocations remain.

3. The method of treating a substantially square tile of porousfiberboard useful as ceiling tile, which tile has a face coat thereon,which comprises compressing the tile with its back on a sphericallyconvex platen by applying a substantially planar platen and therebysubstantially uniformly loading the exposable tile face, whereby duringcompression to deform the tile to a concave back surface correspondingto said convex platen and thereby altering the original stresses in theuncompressed tile and introducing new stresses in the compressed tile,and releasing the tile from said compression.

4. The method of treating a substantially square tile of porousfiberboard useful as ceiling tile, which tile has a face coat thereon,which comprises compressing the tile with its back on a sphericallyconvex platen by applying a heated substantially planar platen embossedwith a design and thereby hot-pressing portions of the surface to inwardlocations and thereby substantially uniformly loading the exposable tileface, whereby during compression to deform the tile to a concave backsurface corresponding to said convex platen and thereby altering theoriginal stresses in the uncompressed tile and introducing 5 newstresses in the compressed tile, and releasing the tile from saidcompression, said inward locations being such that on said release ofcompression inward locations remam.

References Cited in the file of this patent UNITED STATES PATENTS

1. THE METHOD OF TREATING A SUBSTANTIALLY SQUARE TILE OF POROUSFIBERBOARD USEFUL AS CEILING TILE, WHICH COMPRISES COMPRESSING THE TILEONTO A CENTRALLY CROWNED SUPPORTING PLATEN BY APPLYING A SUBSTANTIALLYPLANAR PLATEN AND THEREBY SUBSTANTIALLY UNIFORMLY LOADING THE EXPOSABLETILE FACE, WHEREBY DURING COMPRESSION TO DEFORM THE TILE TO A DISHEDBACK SURFACAE CORRESPONDING GENERALLY TO SAID CROWNED PLATEN AND THEREBYALTERING THE ORIGINAL STRESSES IN THE UNCOMPRESSED TILE AND INTRODUCINGNEW STRESSES IN THE COMPRESSED TILE, AND RELEASING THE TILE FROM SAIDCOMPRESSION.